Uganda said on Monday four policemen patrolling on its side of Lake Albert had been killed by Congolese troops and demanded Kinshasa punish those responsible.
The lake is shared in roughly equal parts by the two countries and has in recent years been the scene of sometimes deadly clashes, mostly over alleged illegal fishing in each other’s waters.
The discovery of commercial oil deposits on the Ugandan side has heightened the tensions, with Democratic Republic of Congo (DRC) sometimes accusing Uganda of conducting illegal exploration in its waters.
The frontier area’s security is also undermined by the lawless nature of DRC’s eastern region where militias roam and Kinshasa’s grip is fragile.
In a statement, Uganda’s Ministry of Foreign Affairs said the four police personnel had been attacked on Saturday by soldiers of the FARDC, the Congolese army, while “on official patrol duty on Lake Albert within the territorial sphere of Uganda”.
Uganda had sent a protest note to Kinshasa and demanded “that the officers of the FARDC who are responsible for the murder … be brought to justice and appropriate compensation to the bereaved families be effected”, the statement said.
Uganda hopes to start pumping crude from the Lake Albert region by 2018.
In 2007 Congolese troops opened fire on a barge belonging to Heritage Oil Corporation (HOC) and a British oil contractor, Carl Nefdt, was shot dead.
DRC accused the company of prospecting for oil in its waters and said its soldiers had acted in self-defence.
HOC then co-owned the fields with Britain’s Tullow Oil but later sold out to its partner.
Uganda estimates it has 6.5 billion barrels of crude reserves in the Albertine rift basin fields.
Tullow, French oil major Total and China’s Cnooc jointly own the fields. Uganda agreed last month to build a crude export pipeline through Tanzania.